This project will link records from the 1940 U.S. Census to records for respondents to the Health and Retirement Study (HRS); the Panel Study of Income Dynamics (PSID); the Wisconsin Longitudinal Study (WLS); the National Social Life, Health, and Aging Project (NSHAP); and the National Health and Aging Trends Study (NHATS). These ongoing longitudinal studies are the cornerstones of America's data infrastructure for interdisciplinary research on aging and the life course; physical and mental health, disability, and well-being; later-life work, economic well-being, and retirement; and end-of-life issues. A crucial limitation of these studies is that they contain little information about social, economic, family, neighborhood, and environmental circumstances in childhood and young adulthood. The sparse early-life information that is now available is usually collected retrospectively in later adulthood; the quality of these few retrospective reports is largely unknown. This serious limitation of these data hinders researchers' ability to study the long-term impacts of childhood and young adult circumstances and to understand how later-life outcomes are the result of cumulative life-course processes. Linking these studies to the 1940 U.S. Census will produce data infrastructure that vastly expands their analytic utility for a variety of substantive problem. This project involves (1) preparing and formatting data files containing respondents' identifying information; (2) deploying sophisticated machine linking algorithms to link the project records to the 1940 U.S. Census; (3) hand linking records that cannot be machine linked and hand-verifying a portion of those that can; (6) creating individual-, family-, and contextual/spatial-leel variables that are consistent with IPUMS and comparable across projects; (7) documenting the new measures and making them available as part of projects' restricted access dissemination systems in a manner consistent with respondents' privacy rights; (8) publicizing the resulting measures and conducting user outreach to maximize the utility and visibility of the new data resource; and (9) conducting methodological analyses to assess the validity of retrospective reports of childhood social and economic circumstances. The project will be led by a team from the Minnesota Population Center in collaboration with each projects' leadership team. The researchers have considerable expertise in the construction and analysis of longitudinal studies of health and aging and in historical record linkage using machine and hand linking techniques.